Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Roller conveyors are universally used for transporting bulk solids, especially bulk particulate material, such as minerals, including coal. Generally, roller conveyors include an endless belt mounted on a series of idler rollers. The endless belt is driven over the idler rollers in operation, the idler rollers supporting the endless belt as well as the bulk solids.
In general, the idler roller includes a roller casing, an internal shaft and a set of bearings for allowing the casing to rotate about the internal shaft. The internal shaft typically extends the full length, or longer than, the length of the idler roller casing. The bearings are provided, in general, close to either end of the roller casing in a two point support configuration. Most idler rollers in service are of this two point support type, called a through-shaft type idler roller.
A disadvantage of this through-shaft type of idler roller is the excess mass of the unit, due to wasted material being needed for the long static shaft. To reduce weight, the shaft and bearings are kept small. However, this leads to significant bending loads being imposed on the shaft and therefore requires bearings to have substantial tolerance for angular error. This in turn compromises the expected life of the bearings and increases the frequency of service and maintenance of each idler roller. This angular displacement also leads to the use of labyrinth seals over lip seals, resulting in a more complex unit.
Another disadvantage is that during operation of the conveyor a considerable amount of dust, moisture and other contaminants is deposited by the bulk solid, around the idler rollers, leading to the ingress of these contaminants past the dust and labyrinth seal into the upper bearing and casing below. This causes increased idler roller drive torque, idler roller failure and even belt damage.
Finally, removal of the through-shaft type from an assembled roller conveyor can be problematic, where the conveyor belt has to be substantially raised in order to lift the shaft ends of the idler roller from their respective support slots in the idler roller frame. This increases the risk of injury during removal, maintenance and replacement of the idler rollers.